In places where traffic volume is low and securing land is easy, roundabouts can be effective.

Prof Hideki Nakamura of Nagoya University, an expert in infrastructure engineering. Roundabout intersections, a common sight in Europe and the United States, are gaining attention in Japan as a means of boosting traffic safety. (Yomiuri Shimbun)

And about time too but it will take a while for people to get used to them.
Many years ago I lived in Kuwait and they changed the rule on roundabouts from vehicles entering the roundabout having priority to the usual vehicles already on the roundabout having priority. Despite signs warning of this change being there for 6 months previous there was mayhem for a week or so.

If it might just possibly curb those who habitually run red lights, I'll be happy to see them.
Roundabouts make for more fluid and quicker movement of traffic anyway. Perhaps part of the reason that so many run red lights here is the knowledge that they'll have to wait a good 2 minutes or more before they can go again. That said, those who do run the red still catch one another 100 metres up the road anyway, so really, I still don't understand them...

fdsFeb. 28, 2013 - 11:44AM JST
... but problem is they take up space which japan doesn't really have.

They don't need to be huge, in fact some I've seen in Ireland and the U.K. are tiny, and do their job quite well. Although I do hope that the Japanese resist the European tendency to plant trees on the roundabouts, because the trees obstruct vision and make it difficult to see pedestrians and other cars. Flowers? Ok. Trees? No.

Oh God please no.. I was thinking about this and what a disaster it would be just the other day when a guy in a car coming towards me at some lights stared at me for a good 5 seconds before turning right, crossing in front of me at the very last second, even though he'd had ages to do so beforehand. He was doing the the head bobbing, staring, like people do when walking, but in his car ffs. No, just turn right as soon as you can and get the hell out of the way. I notice that a lot people wait ages before making their move, then when they do you're 10 metres away and they pull out and turn as fast as an oil tanker with not a thought that the loud screeching sound they can hear is due to their moronic activity.

I can see people doing the same thing on roundabouts, but it's going to be a lot more dangerous. Funnily going through red lights is not actually that dangerous so long as everyone is looking and they don't go until the last car has passed, but I can imagine cars coming on to roundabouts pull out at the very last second, for some reason at just the moment a car on the roundabout is passing them even though they'll have had ages to judge speed and distance but will have only finally got round to making their mind up about going, or cars already on the roundabout will stop and politely bob their heads and let someone come on to the roundabout causing a pile up when everyone behind them plows into them because they weren't expecting it...

They added some roundabouts (we call them "traffic circles") to US Route 15 here in Virginia about 8 years ago. While I can't speak for rush hour traffic, the 7 or 8 times I've gone through them have been painless with almost no delay other than slowing to navigate the roundabout.